The invention relates to a method for cleaning the filters of a vacuum cleaner comprising a dirt collecting container, which has a suction inlet and is in flow connection with at least one suction unit via at least one filter and at least one suction extraction line, and comprising at least one external air inlet which opens into the suction extraction line downstream of the at least one filter and can be closed by means of at least one closing valve, wherein the at least one closing valve has a valve body which is movable back and forth between a closed position and an open position, and is acted upon by a closing spring with a closing force, which valve body lies against a valve seat in the closed position and is at a distance from the valve seat in the open position, wherein, in order to clean the at least one filter, at least one closing valve is opened and the side of the at least one filter that is oriented away from the dirt collecting container is impinged upon by external air.
The invention also relates to a vacuum cleaner for carrying out the method.
By means of the vacuum cleaners in question here, dirt and preferably also liquid can be sucked up using at least one suction unit to apply negative pressure to the dirt collecting container, so that a suction flow forms and dirt and liquid can be sucked into the dirt collecting container. The vacuum cleaners have one or more filters, which are disposed in the flow path between the dirt collecting container and the at least one suction unit and serve for separating solid substances from the suction flow. During suction operation, dirt particles are increasingly deposited on the side of the at least one filter that is oriented toward the dirt collecting container, so that after some time the filter or filters have to be cleaned. For cleaning, the side of the filters that is oriented away from the dirt collecting container can be impinged upon by external air, by opening at least one closing valve, so that external air can flow into the at least one suction extraction line via the external air inlet and impinge upon the side of the at least one filter that is orientated away from the dirt collecting container.
In utility model DE 298 23 411 U1, to clean a filter it is proposed to close for a short time a suction hose that is connected to the suction inlet of the dirt collecting container, so that a strong negative pressure forms in the dirt collecting container, and a closing valve is subsequently to be opened for a short time. The filter is then flowed through by the external air in the direction of counterflow, that is to say counter to the direction of the suction flow that prevails during normal suction operation, so that dirt particles adhering to the filter become detached. As a result, effective cleaning of the filter can be achieved, but for this purpose suction operation must be interrupted by the user.
In DE 199 49 095 A1, it is proposed to use two filters, which are cleaned in turn, it being possible during the cleaning of one filter for the suction operation to be continued to a restricted extent by way of the other filter. However, this requires a complex construction, the two filters having to be of a considerable overall size in order to make an adequate suction flow possible during the unrestricted suction operation. Furthermore, the alternative cleaning of one filter at a time, while at the same time maintaining suction operation by way of the other filter, is in many cases susceptible to faults.
WO 97/19630 A discloses a vacuum cleaner with a dirt collecting container at the suction outlet of which a filter is disposed. For cleaning, the filter can be flowed through by external air counter to the direction of flow prevailing during suction operation. For this purpose, the vacuum cleaner has an external air inlet which opens into the suction extraction line and can be closed by means of a closing valve. The closing valve comprises a valve body which is acted upon by a closing spring with a closing force and in each position lies against a resilient stop element. The force of the stop element, like the spring force of the closing spring, permanently acts on the valve body. To attain its opened position, from its closed position the valve body must immediately overcome both forces.
It is an object of the present invention to provide a method of the type mentioned at the beginning in which all the filters present can be flowed through by suction air during suction operation, but for the user there does not have to be any noticeable interruption in suction operation for filter cleaning.